(1) Field of the Invention
The present invention relates to a hearing aid particularly useful for placement behind an ear of a hard-of hearing person, which comprises a multi-part housing containing electrical hearing aid components, such as a microphone, an audio signal amplifier, an audio signal receiver, a battery and the like, detachable fastening elements for holding the parts of the housing together, and an audio input connection to one of the components.
The audio input connection is an electrical contact arrangement which feeds an electrical audio signal directly, i.e. galvanically, to an amplifier in the housing. Such an audio input is used frequently in schools for hard-of-hearing persons in connection with "multiple hearing devices", or in connection with FM- or infrared radiation transmitters. However, individual head-of-hearing persons may also profit from various auxiliary devices, such as hand-held microphones, TV-adapters, hand-carried cassette players, etc., which may be connected to the audio input.
Electrically, the audio input is an electrical contact device which enables the output cable of an external audio signal source to be connected to the hearing aid by means of a plug-and-pin combination or a pressure contact, for example.
Due to the notorious lack of space in modern behind-the-ear hearing aids, these electrical contact arrangements differ from one manufacturer to the other and frequently even from model to model of the same manufacturer. This has necessitated in hard-of-hearing schools, for example, an unbelievably high number of different cable connections.
(2) Description of the Prior Art
It has been proposed to solve this problem by providing a so-called audio shoe. This is a cup-like structure which is clamped to the lower part of the hearing aid and whose inside carries contact springs adapted to engage individual contact arrangements of the respective hearing aid while its outside defines two or three sockets for a standardized Euro audio plug. Such an audio shoe has been disclosed in German patent No. 2,751,755. Each type of hearing aid requires a specific audio shoe.
In view of the continuing efforts to miniaturize all hearing aids and their components, behind-the-ear hearing aids also are becoming ever smaller, and the most up-to-date constructions have ever less room for contact arrangements for an audio input connection. Therefore, many miniaturized hearing aids are on the market today which have no audio input of the described type and while they are particularly adapted for use by children, their usefulness is accordingly restricted. A possible solution has been proposed by German Utility Model No. 8,319,075, which discloses a plug-in arrangement for the audio input in the form of a "backpack" suspended from the hearing aid. However, this is not a very attractive solution because it increases the overall size of the hearing aid and the "backpack" remains in position even when no audio input is required.